Currently, assays are read by human eye or a high cost imaging system. Assay readings done by eye are based on individual human judgment and therefore are subject to human error. Assays readings done by imaging systems require expensive detection systems. The purpose of reading these assays is to determine whether a test sample of biological or chemical material being assayed includes a particular analyte, or a derivative or constituent of the analyte. The particular analyte that is the subject of the assay is referred to as the analyte of interest. The test sample may include biological material such as urine, saliva, blood plasma, or the like. The test sample may include chemical material such as rainwater, sludge, or the like.
An assay is performed using a substrate having a sensitive region patterned on the surface of the substrate. Such substrates are known in the art, and the sensitive region is formed by a chemical treatment or a physical manipulation of the surface. The pattern of the sensitive region includes one or more shapes, for example, a circular shape with a diameter of approximately one centimeter (cm).
The substrate is typically made of silicon or glass and has a smooth surface. The surface of the substrate includes a sensitive region that reacts to exposure to an analyte of interest. The sensitive region is indistinguishable from the substrate outside the sensitive region until the sensitive region is exposed to the analyte of interest. The sensitive region will react to exposure of the sensitive region to an analyte of interest.
Detection of the reaction of the sensitive region upon exposure to the analyte of interest is performed by human eye or high-cost, high-resolution detection systems that determine the shape of the sensitive region upon exposure to the analyte of interest.
A human observes the sensitive region to determine if exposure to the sample resulted in a change in the appearance of the sensitive region relative to the rest of the substrate. If there was a sufficient change, the observer concludes that the sensitive region was exposed to the analyte of interest and thus, that the analyte of interest was included in the sample. When readings are made by the human eye to determine an exposure of the sensitive region to an analyte of interest, the readings may not be consistent and may be prone to error.
When assays are read by high-resolution systems, such as a charge-coupled device (CCD) systems and some CMOS-based system, the determination of an exposure of the sensitive region to of a analyte of interest is determined by a reading across the entire substrate to determine the shape and location of the sensitive region exposed to the analyte of interest. Such systems may be consistent and relatively error free. However, the equipment is expensive and such detailed determination is unnecessary.
Application Ser. No. 11/019,183 filed by the applicant on Dec. 23, 2004 (also referred to here as the “11/019,183 Application”) describes a low resolution detection system that is strategically arranged in the image plane of a lens to detect illumination from reactive regions in a test assay in which the reactive regions for different analytes have different shapes, such as circular shapes, square shapes and/or rectangular shapes. The detection is done in the image plane of the lens using a priori knowledge of the shape for each reactive material in the test assay.
A market demand exists for a simple, consistent and inexpensive system to determine whether a test sample of biological or chemical material being assayed includes an analyte of interest.